Heretofore, pressure vessels that receive a pressure higher than an atmospheric pressure have been widely used inside containers formed by welding heads to the top and bottom of a shell. Examples of such pressure vessels include a structure in which an end of a plate material is welded and attached to a wall surface member of a shell or a head, such as a bolster plate which is attached so as to partition the inside of a container body and receives a pressure.
FIG. 9 is a sectional view illustrating a conventional structure of a weld structure portion in which a bolster plate is attached by welding to a wall surface member of a pressure vessel. In this weld structure, an end of a plate material 1 is welded to a wall surface member 2 with a weld portion 3 so that a substantially T-shaped sectional surface is formed.
Such a weld portion 3 is subjected to machining so as to obtain an exposed surface 4 that forms a tapered shape, an R-shape, or the like to alleviate a stress concentration on the weld portion.
Note that Patent Literature 1 described below, for example, discloses a technique in which the weld portion 3 described above is subjected to machining into an R-shape.